Frequently Asked Questions

Find answers to the most asked questions about your purchase, order or shipping

Yes. Your ride will drive better than ever because both wheels will receive traction. When things get hot the Spartan Helical LSD will limit wheelspin across the drive axle by permitting the axle shafts to spin at different speeds while continuously trying to balance the application of torque between the two axles. This results in transferring more power to the wheel with the best traction. This improves vehicle control and performance. Mashing the throttle, taking a tight corner aggressively, or working through loose gravel or challenging sections of trail will actuate the unit’s gear array to increase your traction.

Check out our “Unboxing the Spartan Helical LSD” and “The Spartan Helical LSD by USA Standard” videos for more information on LSDs.

Unboxing the Spartan Helical LSD

The Spartan Helical LSD by USA Standard

In its static state a limited-slip is pre-loaded and provides traction to both wheels. When the LSD is further loaded… under acceleration, in a fast corner, or when wheel slippage occurs off-road… the clutch packs limit wheelspin across the drive axle by permitting the axle shafts to spin at different speeds while continuously trying to balance the application of torque between the two axles. This results in transferring more power to the wheel with the best traction.

Learn more about limited slip differentials in our How It Works blog article here.

Watch our “Are Posis Worth It?” video to get more info about limited-slip differentials.

Are Posis Worth It?

We predominantly use five metal types; 4320, 4340, 8620, 9310, and 1541H.

4300-series is a nickel-chromium-molybdenum alloy, i.e. chromoly, that’s low in carbon content. 4320 is used for the internals in our line of Yukon Dura Grip LSDs. We use 4340 in the manufacturing of forged gears, pinion gears, high-performance axles, Super Joints, and more. 8620 is a low-nickel alloy steel generally used in the manufacture of forged camshafts, crankshafts, and fasteners. We use it in gears and cases. 9310 is an alloy steel with more nickel and chromium than 8620. 9310 can better endure high shock loads without failing and we use it in Spartan Lockers. 1541H is a high-grade carbon steel used in our replacement axles and u-joints, and similar products. A caveat here, heat-treating plays a definitive role in a given alloy’s hardness and other properties that impact their performance in automotive drivetrain applications. We use advanced heat-treating techniques to fine tune our alloys to their intended usage.

Using non-synthetic 80W-90 GL-5 will produce optimum performance.

Learn more about LSD oils, and drivetrain lubrication in general, by watching our “Tech Talks, Oils and Additives” video.

Tech Talks, Oils and Additives

When traveling in a straight line where wheel speeds are identical on both sides, all LSDs continuously provide equal traction to both tires. The difference between LSD types has to do with how this occurs and what happens when additional traction is needed.

In a clutch-type unit, the spring array applies pressure to the side gears which puts pressure on the clutch packs in the outer part of the carrier. Both axles get equal pressure and both tires get equal traction. When a tire starts slipping, the clutch packs are engaged with different resistance. The clutches work to maintain synchronization between the tires, transferring more torque to the tire that has the best grip while reducing torque transfer to the tire that has less grip.

A gear-type LSD has no frictional surfaces to initiate torque transfer. It uses floating helical-cut worm gears that operate in pockets and mesh together. Under normal driving conditions this type of LSD acts like an open diff. When acceleration or wheel slippage occurs, axial and radial thrust is applied to the helical gear pinions in their pockets. Under these loads, more torque is transferred to the tire with the best traction in a progressive manner as torque is withheld from the tire that is slipping.

First, this product is for clutch-type differentials only, not gear-driven limited slips like our Spartan Helical LSD. Friction modifiers are all about chatter. They guard against abnormal clutch engagement and/or disengagement (source of the chatter), ensuring the proper friction characteristics between clutch discs are maintained.

Some are, some aren’t.

Clutch-type LSDs, like our Dura Grip, can be rebuilt. Rebuilding involves replacing the clutches in the unit. The clutches can be replaced to bring the unit back to its original performance level, or non-stock clutches with different friction characteristics and springs with custom compression rates can be used to fine tune the Dura Grip’s performance to better match the style of driving/racing you are doing.

Gear-type LSDs, like our Spartan Helical, do not require rebuilding because there are no clutches to replace, there is nothing to rebuild. The unit’s internal worm gears should last the life of your vehicle.

Lockers produce 100% lock-up where all the power is directed to both tires all the time when the unit is engaged. Lockers are tougher. Limited slips direct torque to both tires and when slippage occurs directs torque to the tire with the best traction. LSDs do not generate 100% lock-up. Limited-slip diffs do not require activation from the driver. Their engagement is mechanical, a reaction to driving conditions, namely load and wheel slippage.

Learn more about the features and benefits of different Yukon and USA Standard Gear traction devices by checking out our “Which Traction Device is Right for You?” video.

Which Traction Device is Right for You?